Array configuration

32

32

Array sizeb

33.6±0.1 mm

39.0±0.1 mm

Horizontal

Vertical

Effective focal lengthc

5.17±0.12 m

5.03±0.13 m

Primary illuminationc

5.60±0.21 m

5.59±0.23 m

Focal ratioc

0.93±0.02

0.90±0.02

Detector spacing

41±4″

50±4″

Optical Properties: 277 GHz Array

Horizontal

Vertical

Effective focal lengthc

5.41±0.11 m

5.06±0.12 m

Primary illuminationc

5.48±0.19 m

5.50±0.20 m

Focal ratioc

0.98±0.04

0.91±0.04

Detector spacing

40±4″

49±4″

aHorizontal error estimated from fabrication tolerances. Vertical error estimated from machining tolerances.bErrors are estimated from machining and assembly tolerances.cThe number varies across the array and the "±" indicates the maximum and minimum of the range.

PROPERTIES OF THE MBAC FILTERS

Array

148(GHz)

218(GHz)

277(GHz)

Comp. Bandcentera

146.9

217.3

273.5

Max. Transmissiona

0.74

0.72

0.69

Bandcenterb

149.2±3.5

219.7±3.5

277.4±3.5

Bandwidthb

18.4

17.0

20.9

Noise Bandwithb

27.6

25.9

34.8

Band FWHMb

27.0

22.2

30.3

Effective Bandcentersc

Synchrotronc

147.6

217.6

274.8

Free-freec

147.9

218.0

275.4

Rayleigh-Jeansc

149.0

219.1

276.7

Dusty Sourcec

149.7

219.6

277.4

CMBc

148.4

218.3

274.7

SZ Effectc

146.9

220.2

277.2

Conversion factors

δTCMB ⁄ δTRJ

1.71±0.04

3.02±0.10

5.44±0.20

δW ⁄ δTRJ (pW ⁄K)

0.569±0.055

0.483±0.055

0.699±0.055

Γ (μK ⁄Jy)

6826±350

5824±240

4373±550

aBased on a composite of room temperature measurements. The source spectrum has been divided out. The effect of the lenses and coupling to the detectors is not included.bMeasurements were made with all filters installed in MBAC along with the lenses and the ACT detectors. This measurement includes neutral density filters in each band and the coupling of the FTS to MBAC. The neutral density filters are not present when observing the sky. Three measures of the width of the band are given. The uncertainties are obtained from a combination of the rms of the measurements and an estimate of the systematic er- ror. The source spectrum has been divided out of the measured response.cEffective band centers for synchrotron emission (α = -0.7), free-free emission (α = -0.1), Rayleigh-Jeans emission (α = 2.0), dusty source emission (α = 3.5). These values are based on the average of the computed composite of all filters and the measured response in MBAC. The uncertainty on all values is 3.5 GHz. For example, for the response to the CMB we use 148 GHz, 218 GHz in AR1 and AR2. Since the CMB will be difficult to detect in AR3 we use the RJ band center of 277 GHz.

DETECTOR PARAMETERS

Array

G

(pW/K)

Tc

(mK)

Dark Noise

(W ⁄ √Hz)

τ

(ms)

148 GHz

80±20

510±20

(6±2)x10-17

1.9±0.2

218 GHz

120±30

510±20

(5±1)x10-17

2.5±0.4

277 GHz

300±60

500±30

(7±1)x10-17

1.6±0.3

SUMMARY OF BEAM PARAMETERS

148GHz

218GHz

277GHz

Solid Anglea (nsr)

217.7±3.6

117.6±2.8

97±12

Major FWHMa (′)

1.401±0.003

1.012±0.001

0.891±0.04

Minor FWHMa (′)

1.336±0.001

0.991±0.001

0.858±0.005

Axis Anglea (°)

66±1

45±2

66±10

aThe error bars are effective 1- errors. The relatively large size of the 277 GHz error bar is due to the systematic errors from atmospheric modeling and is expected to improve.